A major objective of the present invention is to improve on the tool disclosed in U.S. Pat. No. 4,373,380, Mayo. In accordance with the present invention, the utility of the patented tool has been greatly expanded, while its structure has been considerably simplified and its manufacturing cost reduced.
These important improvement features result mainly from the fact that the outside diameter of the improved tool has been substantially reduced in comparison to the outside diameter of the patented tool. As a result of this diameter reduction, the improved tool is not limited in its usage to testing internal sealing surfaces of relatively large diameter well head housings. The improved tool can be used to test the integrity of relatively smaller diameter well casings and other sleeve members.
The casing, casing hanger and connecting joints immediately below the blow-out preventer (BOP) or well head can fail during well drilling operations. Such failures are responsible for a number of very costly blow-outs. The U.S. Minerals Management Service does not presently require testing of well components below the casing hanger, and heretofore this area of the well, as a practical matter, could not be tested. The present invention satisfies a need for a practical and economical test tool for the zone of a well below the casing hanger.
A further objective of the invention is to provide a multipurpose tool which can be used to isolate members of the well head, BOP and hanger assembly for testing.
In accordance with this invention, the improved tool has four main functions:
1. As an isolation tool, the unit can be run in 183/4", 163/4" and 135/8" BOPs to determine leakage in these components.
2. The tool can test an intact sub-sea well head housing which has been used or repaired and will provide a graphic chart of the test as a permanent record in the manner disclosed in U.S. Pat. No. 4,373,380. This enables an operator to make a decision on scrapping or reconditioning a used well head housing so that the useful life of the same can be extended.
3. The tool according to the present invention can replace cup-type testers. Its seals are much more durable and will far outlast cup-type seals which are subject to damage as they are pulled from the well.
4. The improved tool serves as a key seat indicator tool. The relatively thin lips of metal containment rings for elastic seal elements indicate key seat wear present in well casings by bulging outwardly into key seat recesses under influence of fluid pressure. An operator observing this condition can reposition the drilling pipe or mobile rig before key seat wear in one location has become too great to tolerate.
Other features and advantages of the invention will become apparent to those skilled in the art during the course of the following detailed description.